EVOH Resin Composition Moisture Resistance Retort Packaging
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Solution Overview
Problem
Ethylene-vinyl alcohol copolymer (EVOH) gas barrier properties are compromised at high humidity and temperature conditions, leading to 'retort shock' during food retorting, and desiccant particles are difficult to disperse uniformly, resulting in agglomerates that degrade gas barrier properties and container appearance.
Innovation Solution
A resin composition comprising EVOH with a high ethylene content and a phosphoric acid salt that forms a hydrate, combined with a dispersing agent such as glycerol monostearate, which improves moisture resistance and dispersibility, preventing agglomerate formation and maintaining gas barrier properties during retort treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If desiccant particles are added to EVOH matrix, then gas barrier properties are improved, but particle dispersion uniformity deteriorates causing agglomerates
Solution Approach 1:
A graft copolymer serving as a dispersing agent is introduced as an intermediary between the desiccant particles and EVOH matrix. This dispersing agent contains both polar groups that interact with inorganic particles and non-polar groups that are compatible with the polymer matrix, enabling uniform dispersion and preventing agglomerate formation while maintaining gas barrier properties.
2Reliability
If EVOH is used as barrier resin, then gas barrier properties are improved, but moisture resistance at high humidity deteriorates causing retort shock
Solution Approach 1:
Inorganic desiccant particles are introduced as intermediaries to absorb moisture within the EVOH matrix, preventing water from acting as a plasticizer. This maintains the hydrogen bonding network and free volume structure of EVOH even at high humidity, preventing retort shock and maintaining gas barrier properties.
Solution Approach 2:
The water content within the EVOH matrix is controlled by adding desiccant particles, changing the moisture parameter to prevent plasticization. This maintains the physical and chemical properties of EVOH under high humidity conditions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The resin composition effectively maintains gas barrier properties under high temperature and humidity conditions, preventing oxidation degradation of food products and reducing the frequency of extruder screen exchanges by ensuring uniform dispersion of desiccant particles.
Implementation Method 1
a phosphoric acid salt (B) which can form a hydrate
Implementation Method 2
a dispersing agent (C), wherein the dispersing agent (C) comprises at least one species selected from the group consisting of aliphatic acid salts, glycerol aliphatic acid esters and aliphatic acid amides
Data Source
AI summary
To provide a resin composition comprising an ethylene-vinyl alcohol copolymer (A) having an ethylene content of from 15 to 65 mol % and a degree of saponification of 95 mol % or more, a phosphoric acid salt (B) which can form a hydrate, and a dispersing agent (C), wherein the dispersing agent (C) comprises at least one species selected from the group consisting of aliphatic acid salts, glycerol aliphatic acid esters and aliphatic acid amides, the resin composition comprises (A) and (B) in amounts of from 50 to 99 parts by weight and from 1 to 50 parts by weight, respectively, based on 100 parts by weight of (A) and (B) in total, and the resin composition comprises (C) in an amount of from 1 to 20 parts by weight based on 100 parts by weight of (B). This resin composition excels in gas barrier property and also in moisture resistance at high temperatures and high humidities. Therefore, it is suitable for food packaging containers to be retorted.